In the production of galvanically coated steel strips, for example, in the production of tin plate, a method is known for increasing the corrosion resistance of the coating by a melting of the coating according to the galvanic coating process. To this end, the coating deposited galvanically on the steel strip is heated to a temperature above the melting point of the coating material and subsequently quenched in a water bath. By the melting of the coating, the surface of the coating receives a shiny appearance and the porosity of the coating is reduced, wherein its corrosion resistance increases and its permeability for aggressive substances, for example, organic acids, is reduced.
The melting of the coating can, for example, take place by means of inductive heating of the coated steel strip or by electric resistance heating. From DE 1 277 896, for example, a method for increasing the corrosion protection of metallized iron strips or plates is known, in which the metallic coating is melted by an increase to a temperature above the melting temperature of the coating material and is exposed to high-frequency oscillations during the crystallization process, in the range between the melting temperature and the recrystallization temperature. From DE 1 186 158-A, an arrangement for the inductive heating of metallic strips for the melting of, in particular, electrolytically applied coatings on steel strips is known.
With the known methods for the melting of metallic coatings on steel strips or plates, the entire steel strip or plate, including the applied coating, is as a rule heated to temperatures above the melting temperature of the coating material and subsequently again cooled to a normal temperature, for example, in a water bath. For this, a considerable consumption of energy is required.